The butt of countless jokes about clogged arteries and an early grave, this rich, rendered, onion-scented chicken fat is synonymous with the heavy, plodding food of the shtetls. Even now, as medical science has given a nod to the moderate consumptionof saturated animal fats, and the culinary elite has fallen hard for the likes of lard, tallow and duck fat, poor schmaltz remains the babushka-clad cousin not invited to the table.

This is a shame, because schmaltz is one the most versatile and flavorful fats you can use. Imagine the gentlest of butters infused with the taste of fried chicken, but with a fluffy lightness that melts in the mouth. When it’s properly made, schmaltz has a brawny, roasted character that comes from the bits of poultry skin that brown in the pan. (Those crunchy, golden fried pieces of skin are called gribenes, and they are an addictive snack in their own right.)

Some cooks brown onions in the fat as it renders, which adds a layer of honeyed sweetness. Without the onion, schmaltz is subtle and nutty. Either way, it is the most divine thing you can spread on toasted challah sprinkled with sea salt, and it is excellent for roasting vegetables.

It is also the backbone of Central and Eastern European Jewish cooking. A Yiddish word that actually refers to rendered poultry skin of all kinds (goose, chicken or duck), schmaltz is a staple ingredient for matzo ball soup, chopped liver and latkes. And it was schmaltz, not olive oil, in which Hanukkah latkes were fried. The holiday may be known as the miracle of oil, but for many Ashkenazi Jews, the celebration was fueled by poultry fat.

“Eastern European Jews were using schmaltz for latkes because that’s what they had,” said Rabbi Deborah Prinz, who studies Jewish foodways. Those communities raised geese, chickens and ducks, but not pigs, which are not kosher. (They also made butter from cow’s milk, but were prohibited by religious law from using it in a meal that also contained meat.)

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CreditAndrew Scrivani for The New York Times

Middle Eastern Jews traditionally do use oil for Hanukkah, but they don’t make latkes, added Rabbi Prinz, who noted that doughnuts are the holiday custom in Israel.

Frying latkes in olive oil grew in popularity in the United States in the 1980s, when home cooks started using olive oil more often in general, for health reasons. But by then schmaltz had been in decline for decades, after Jewish immigrants in America discovered cheap hydrogenated vegetable oils.

“Crisco was the number one factor in helping Jews assimilate into American society in the 1920s and ’30s,” said Tina Wasserman, the former food columnist of ReformJudaism.org and author of “Entrée to Judaism: A Culinary Exploration of the Jewish Diaspora.”

“Putting Crisco in a pan and watching the solid white fat melt is identical to watching schmaltz melt, so it was familiar,” she said. “It was assumed to be the cleaner, modern way to cook.”

The fall of schmaltz was cemented with the cholesterol scare of the 1970s, which turned the wonderfully rich substance into a punch line.

But schmaltz has persisted, and in certain quarters you can catch the oniony whiff of a comeback.

The food writer Michael Ruhlman said he decided to write his 2013 cookbook “The Book of Schmaltz” because, after years of vilification, many people were scared to eat it. Mr. Ruhlman, the rare schmaltz proponent who is not Jewish, fell in love with it after trying it with a neighbor, who then gave him lessons in making it.

“I got tired of hearing people talk about schmaltz as a ‘heart attack on the plate,' ” he said.

For Noah Bernamoff, an owner of the Mile End restaurants in New York, embracing schmaltz meant rebelling against his parents’ generation, which passed over homemade schmaltz in favor of hydrogenated margarine. “They had a screwed-up idea of what was healthy and what wasn’t,” he said.

Now he takes pride in using schmaltz as much as possible at his restaurants. He fries with it, spreads it on challah, grinds it into chopped liver, drizzles it into soup and garnishes roasted vegetables and chicken salad sandwiches with the gribenes.

“We use a disgusting amount of schmaltz,” said Mr. Bernamoff with love. “It has a richness you don’t get with vegetable oil.”

When the chef Eric Korsh was a young line cook at Picholine, he never thought of the duck fat he was using for confit as anything but classically French. Later, when he was responsible for bringing down the food costs in a different restaurant kitchen, he came up with what he thought was a novel solution.

“I started buying whole chickens instead of packaged breasts, and then I’d render the fat,” he said. “You save so much money this way, and having all this beautiful poultry fat on hand gives you a lot of options.”

Now, as the chef at North End Grill in Battery Park City, Mr. Korsh renders the fat from both ducks and chickens and uses it for charcuterie, confit and some of the city’s best French fries. It wasn’t until he recalled his visits to Lower East Side delis with his Jewish grandfather that he made the connection: He had been making schmaltz all along.

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CreditAndrew Scrivani for The New York Times

Although rendering poultry fat is a simple task for chefs, the technique is a lost art for many home cooks. To help remedy this, Alana Newhouse, the editor of Tablet magazine, has an annual schmaltz-making party at her home in Brooklyn that she calls the “schmixer.”

Not only does she show people how to make traditional schmaltz, she also encourages guests to flavor individual batches with herbs, spices and even chiles. Everyone takes home a small Mason jar of the gorgeous fat.

All her guests love it. “One can easily peg this to nostalgia, and maybe that’s part of it,” Ms. Newhouse said. “But it’s also real engagement.”

She added that the newfound interest in schmaltz may parallel the resurgence of interest in tradition among Jews in their 20s and 30s, who, unlike their immigrant forebears, are not afraid that a display of Jewishness is a threat to their American identity. And schmaltz is delicious, which can come as a surprise to the uninitiated.

But the real showstoppers at the party, Ms. Newhouse said, are the gribenes, which guests wash down with shots of slivovitz, Eastern European plum brandy.

An article on Dec. 10 about the new popularity of schmaltz among restaurant chefs and home cooks omitted part of the title of a 2013 cookbook by Michael Ruhlman. It is “The Book of Schmaltz,” not merely “Schmaltz.”